1. Field of the Invention
The present invention relates to a power circuit.
2. Description of the Related Art
An example of a regulator discharges an electric charge in a capacitor connected with an output terminal in order to quickly reduce an output voltage (for example, Patent Document 1).
FIG. 1 is a circuit diagram of a regulator disclosed in Patent Document 1. A transistor Q controlling an output voltage Vo is connected between an input terminal 1 and an output terminal 2 in series. A direct-current source E1 is connected to the input terminal 1 so as to supply an input voltage Vi. A capacitor C1 is connected to the output terminal 2.
When a transistor Q1 is in a stopped state (an off state), a switch circuit 4 stops a supply of a base current from a constant current source S1 to a transistor Q2. Therefore, the transistor Q2 is turned off so as to shut off a detection circuit 6 detecting the output voltage Vo. A current flowing through resisters R1 and R2 becomes a base current of a transistor Q4, and this base current is amplified twice (is provided with a two-stage amplification) by the transistors Q4 and Q5 so as to become a base current of a transistor Q3. Then, the electric charge of the capacitor C1 is discharged by the transistor Q3. Therefore, the output voltage Vo is reduced.
[Patent Document 1] Japanese Laid-open Patent Publication No. 2000-66742